Dynomotion

Group: DynoMotion Message: 11482 From: fchopinqc Date: 5/8/2015
Subject: Linear close loop control with KFLOP
Hi everyone, what would be your choice if you want to use linear encoder strips for a close loop contro XY stage with Kflop.

Optical (aka US digital) or magnetic?

maximum speed 300mm/s

should I go with differential data lines or not?

How many CPI would you suggest? can KFlop take 2000CPI a 300mm/s?
Group: DynoMotion Message: 11483 From: fchopinqc Date: 5/8/2015
Subject: Re: Linear close loop control with KFLOP
further more is it necessary to go with a dual loop system when using step motor 400 steps /Rev ?

and lastly If I must use a dual loop solution what is the best ratio between the motor encoder and stages encoders (is it supported in KFLOP+STEP system?)

Thanks!
Group: DynoMotion Message: 11484 From: Tom Kerekes Date: 5/8/2015
Subject: Re: Linear close loop control with KFLOP
I think optical scales are usually much more accurate because they are based on something like 20um lines vs 2000um magnets.  But magnetic has the advantage of being more rugged and reliable in dirty environments.

Differential are always preferred because they have less noise succeptibility and you can connect them to either single ended or differential inputs.  KFLOP itself only has single ended inputs.

300mm/s x 1inch/25.4mm x 2000 cycles/inch x 4 quadrature counts/cycle = 94KHz which is well below KFLOP's 1MHz max count rate.

HTH
Regards
TK

Group: DynoMotion Message: 11485 From: Tom Kerekes Date: 5/8/2015
Subject: Re: Linear close loop control with KFLOP
I don't think dual loop is normally necessary with Stepper Motors because Steppers inherently provide some position control at the motor shaft without feedback (unlike servo motors).  So for example while moving the motor through any backlash, where the scales are not providing any feedback, the motor is still able to move in a somewhat controlled manner.  Where a servo would tend to unpredicatbly break free from stiction and accellerate uncontrollably.  But it of course depends on your system and requirements.

HTH
Regards
TK